Alpha-Adrenergic receptors and prostaglandin receptors are being studied in human blood cell preparations. The ability of adrenergic agonists to inhibit adenylate cyclase is used as a measure of the Alpha2-receptors' biological function. Binding of tritiated Alpha-adrenergic receptor antagonists to membrane receptors on platelets is being measured. These correlative measures are used to assess Alpha-adrenergic physiological function in normal human beings, patients with various psychiatric disorders, and patients receiving different psychopharmacologic agents.